Periodic triggering of an inducible gene for control of a wild population

A possible method of control for the management of wild populations consists of continual introgression of an inducible transgene by releasing transgenic individuals, with periodic exposure of the population to a trigger. Exposure to the trigger causes death or sterility in carriers of the transgene, but is otherwise benign. We investigate the effectiveness of various strategies for control. We show that suppression of the population density below any pre-specified level is possible using this technique. At the same time we show that too frequent or too efficient exposure to the trigger can select for non-transgenic genotypes at an intensity such that the population density will be largely unaffected by the trigger. Choices for management parameters can ensure that the latter scenario is avoided. We show that releasing individuals carrying the transgene at more than one locus facilitates density control.     

Longitudinal studies on human schistosomiasis

A major difficulty in understanding the epidemiology of human schistosomiasis has been to distinguish between acquired immunity and reduced exposure as possible reasons for an observed decline, in older individuals, of levels of superinfection or of reinfection after chemotherapy. A series of studies of Schistosoma mansoni infections in Kenya has been undertaken to approach this problem, by investigation of intensities of reinfection after treatment of individuals whose levels of contact with contaminated water is subsequently observed. Intensities of reinfection are highest among younger children, thereafter declining sharply. This decline can be attributed only in part to age-related changes in the duration and nature of exposure; there is also evidence for the development of an acquired resistance to reinfection that is dependent both on age and on previous experience of infection, and that may be immunologically mediated. Evidence has been obtained that the slow development of this acquired immunity with age may be associated with the early development and subsequent slow decline of inappropriate immune responses that 'block' the effect of potentially protective responses. Implications of these findings for immunological intervention through vaccination are discussed.     

A genetic selection for temperature-sensitive variants of the gene V protein of bacteriophage f1.

Complementary negative and positive genetic selections based on the activity of a plasmid-encoded bacteriophage f1 gene V are developed. The negative selection is based on an activity of the gene V protein in E. coli cells which markedly reduces the infection of those cells by f1-related viruses. In order to select against cells expressing active gene V protein, the cells are infected with the p'age R386, a derivative of f1 which confers resistance to chloramphenicol, and are plated in the presence of the antibiotic. Those cells which contain gene V protein are infrequently infected with the virus and are unable to grow in the presence of chloramphenicol; those which do not contain the gene V protein are readily infected and can grow in the presence of the antibiotic. The positive genetic selection consists of excising the gene V sequences from the plasmids and using them to replace the gene V of a bacteriophage f1 derivative containing an amber mutation in gene V. Only those genes which encode an active gene V protein can support phage growth and yield plaques. The two genetic selections can be combined in order to yield a substantial enrichment for genes encoding temperature-sensitive gene V proteins.     

Gene X of bacteriophage f1 is required for phage DNA synthesis. Mutagenesis of in-frame overlapping genes

The gene II protein of bacteriophage f1 is a site-specific endonuclease required for initiation of phage viral strand DNA synthesis. Within gene II is another gene, X, encoding a protein of unknown function identical to the C-terminal 27% of the gene II protein, and separately translated from codon 300 (AUG) of gene II. By oligonucleotide mutagenesis, we constructed phage mutants in which this codon has been changed to UAG (amber) or UUG (leucine), and propagated them on cells carrying a cloned copy of gene X on a plasmid. The amber mutant makes no gene X protein, and cannot grow in the absence of the complementing plasmid; the leucine-inserting mutant can make gene X protein, and grows normally without the plasmid. Without gene X protein, phage DNA synthesis (particularly viral strand synthesis) is impaired. We discuss this finding in the context of other known in-frame overlapping genes (particularly genes A and A* of phage phi X174), many of which are also involved in the specific initiation of DNA synthesis, and suggest applications for the mutagenic strategy we employed.     

Prediction of Visceral Adipose Tissue Using Air Displacement Plethysmography in Children

Objective: To determine the ability of air displacement plethysmography (ADP) to predict visceral adipose tissue (VAT) volume in children. Research Methods and Procedures: Fifty‐five (33 boys/22 girls) white children 13 to 14 years old were studied. Anthropometric measures were collected for body mass, stature, BMI, and waist‐to‐hip ratio (WHR), and body fat percentage was estimated from triceps and subscapular skinfolds, bioelectrical impedance analysis, and ADP. VAT volume was determined using magnetic resonance imaging, using a multiple slice protocol at levels L1 to L5. Results: Boys had significantly (p ≤ 0.05) less VAT volume than girls [645.1 (360.5) cm³ vs. 1035.8 (717.3) cm³]. ADP explained the greatest proportion of the variance in VAT volume compared with the other anthropometric measures. Multiple regression analysis indicated that VAT volume was best predicted by ADP body fat percentage in boys [r² = 0.81, SE of the estimate (SEE) = 160.1, SEE coefficient of variation = 25%] and by WHR and BMI in girls (r² = 0.80, SEE = 337.71, SEE coefficient of variation = 33%). Discussion: Compared with the other anthropometric measures, ADP explains the greatest proportion of the variance in VAT volume in children 13 to 14 years old. For boys, ADP is the tool of choice to predict VAT volume, yet using the more simply collected measures of BMI and WHR is recommended for girls. However, large SE of the estimates remained, suggesting that if precision is needed, there is no surrogate for direct imaging of VAT.     

Diversity in the practice of district ethics committees.

A survey of ethics committees in district health authorities was carried out to find out the size and make up of committees and what information and guidance they offered to scientists who apply to do research. A sample (n = 28) of committees in England (n = 190), half from teaching districts and half from non-teaching districts, was contacted by post requesting this information. A high degree of diversity was found, not only in the methods that committees used but also in the ethical criteria each considered to be pertinent for research. It was also shown that published guidelines have made little impact. It is suggested that issuing more guidelines will be of limited use. Rather, the following are needed: information about why guidelines have been widely ignored, better communication between committees, some form of education for committee members, and a formal register of committees compiled.     

Tumor Cell Expression of Vascular Endothelial Growth Factor Receptor 2 Is an Adverse Prognostic Factor in Patients with Squamous Cell Carcinoma of the Lung

A robust immunohistochemical (IHC) assay for VEGFR2 was developed to investigate its utility for patient tailoring in clinical trials. The sensitivity, specificity, and selectivity of the IHC assay were established by siRNA knockdown, immunoblotting, mass spectrometry, and pre-absorption experiments. Characterization of the assay included screening a panel of multiple human cancer tissues and an independent cohort of non-small cell lung carcinoma (NSCLC, n = 118) characterized by TTF-1, p63, CK5/6, and CK7 IHC. VEGFR2 immunoreactivity was interpreted qualitatively (VEGFR2 positive/negative) in blood vessels and by semi-quantitative evaluation using H-scores in tumor cells (0–300). Associations were determined among combinations of VEGFR2 expression in blood vessels and tumor cells, and clinico-pathologic characteristics (age, sex, race, histologic subtype, disease stage) and overall survival using Kaplan-Meier analyses and appropriate statistical models. VEGFR2 expression both in blood vessels and in tumor cells in carcinomas of the lung, cervix, larynx, breast, and others was demonstrated. In the validation cohort, 99/118 (83.9%) NSCLC tissues expressed VEGFR2 in the blood vessels and 46/118 (39.0%) showed high tumor cell positivity (H-score ≥10). Vascular and tumor cell expression were inversely correlated (p = 0.0175). High tumor cell expression of VEGFR2 was associated with a 3.7-fold reduction in median overall survival in lung squamous-cell carcinoma (SCC, n = 25, p = 0.0134). The inverse correlation between vascular and tumor cell expression of VEGFR2 and the adverse prognosis associated with high VEGFR2 expression in immunohistochemically characterized pulmonary SCC are new findings with potential therapeutic implications. The robustness of this novel IHC assay will support further evaluation of its utility for patient tailoring in clinical trials of antiangiogenic agents.